Acrolein is a simple unsaturated aldehyde compound which includes incomplete reactive groups to have high reactivity, and is used as a major intermediate for synthesis of numerous chemicals. In particular, acrolein has been widely used as an intermediate for synthesis of acrylic acids, acrylic acid esters, superabsorbent polymers, animal feed supplements, or food supplements.
Such acrolein has been mainly prepared by selective gas-phase oxidation of a starting material, propylene, which is obtained during petroleum cracking with atmospheric oxygen. However, as fossil fuels have been reduced and environmental problems such as the greenhouse effect have emerged, many studies have been conducted to develop a method of preparing acrolein using non-fossil fuel-based renewable materials.
Therefore, glycerin, which is a natural by-product obtained from biodiesel production, has received much attention as a raw material for acrolein preparation. In particular, the growth of biodiesel production increases the glycerin market, and industrial application of glycerin has been studied due to its low price.
For example, a method of obtaining a mixture of acrolein and acrylic acid by glycerin dehydration in the presence of a catalyst is known. The glycerin dehydration is performed by gas-phase oxidation in the presence of a catalyst, and use of the catalyst is essential. However, the previous catalysts used for the preparation of acrolein produce by-products such as hydroxypropanone, propane aldehyde, acetaldehyde, acetone, and polycondensation products of glycerin, or cyclic glycerin ether, and thus there are limitations in their use for the preparation of acrolein with high purity. In addition, the previous catalysts produce phenol or a polyaromatic compound as a by-product, which problematically causes coke formation on the catalyst and catalyst deactivation.
Accordingly, there is a demand to develop a catalyst system capable of maintaining high catalytic activity during reaction while minimizing formation of by-products causing such problems so as to increase selectivity and purity of acrolein and improve glycerin conversion ratio and reaction yield.